Guinea pig relatives
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Wild guinea pig ( Cavia aperea ) |
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| AE Wood , 1955 |
The guinea pig relatives (Caviomorpha) are a group of diverse rodents belonging to the porcupine relatives that originally occur exclusively on the American double continent.
features
The great diversity of the guinea pig relatives, which is unique within the rodents, is a consequence of the long isolation of the South American continent and the large number of ecological niches it occupies. The group includes many smaller species, but with the Capybara it is also the largest living rodent in the world. Some species have silky, soft fur, others are equipped with bristly hair that has often developed into spikes. Some animals are reminiscent of rabbits, others are similar to rats, and still others have their own appearance.
The teeth show the toothless gap between the incisor teeth and molars , which is typical for rodents . The upper and lower jaws contain one incisor tooth that will grow back over the life of their life, as well as one front and three rear molars per jaw half . As in all rodents, canines are absent. The tooth formula is 1 0 1 3 = 20.
Way of life
Most guinea pig relatives live on the ground, while others live in trees, underground or in water. They are almost exclusively herbivores, but some also feed on insects and larger prey. The grass-eating species are considered the South American counterpart of the ungulates, which are important for the African ecosystem . There are species that live both individually and in large colonies.
The gestation period is usually long, there are only a few kittens per litter and the development stage at birth is quite high. The offspring of larger species are born with their fur and eyes open; many young animals can walk after just a few hours and are independent of the mother a short time later.
Occurrence
Except for Urson , which also occurs in Canada and the USA , the guinea pig relatives are limited in their natural range to South and Central America, including the West Indies . The beaver rat has also been introduced outside of this area. They are found in a wide variety of habitats: forests and grasslands, river banks and rocky deserts, coastal plains and high mountains.
Some species are common, some have long been extinct, and others have only recently been eradicated by humans. He hunts many guinea pig relatives because of their meat or fur; some species are considered pests or disease carriers. The natural predators of the larger species ( pakas , agoutis , capybaras , pakarana and viscacha ) include large and medium-sized predators such as jaguars , ocelots , pampas , maned wolves , forest dogs and South American foxes .
Prickly
The tree spines (superfamily Erethizontoidea) are larger rodents, the back hairs of which have developed into spines and which externally resemble porcupines. They are spread over almost the entire American double continent with the exception of the offshore islands. They only consist of the tree prick family to which the bristle tree prick are also included here .
Guinea pigs
The guinea pig-like (superfamily Cavioidea) are medium-sized to large rodents with a head trunk length of 22.5–130 cm, which are adapted to running. The rib cage is more or less keel-shaped, the sternum is narrow and the collarbone has receded. With the exception of the actual guinea pigs , the limbs are slender and high with keels at the main joints. The lateral front and rear toes tend to recede. Because of their more or less hoof-like claws they were also called "hoof paws" in the past. The tail is short or stubby. This group includes the pakas , the agoutis and acouchis as well as the guinea pigs . They are common throughout South and Central America, but not in the West Indies.
Chinchillas
The chinchilla-like (superfamily Chinchilloidea) include the quite different pakaranas and chinchillas . They are larger rodents found in western and southern South America.
Truffle-like
The truss-like (superfamily Octodontoidea) are outwardly rat-like, small to medium-sized rodents. These include chinchilla rat , octodontidae , tuco-tuco , echimyidae , coypu and tree rats . They are native to all of South America and the West Indies. Only the beaver rat has recently been introduced to North America and Europe by humans.
Development history and systematics
Development history
The guinea pig relatives presumably descend from porcupine relatives who were widespread in the Old World , especially in Africa , and whose descendants still live there today as sand diggers , rock rats and cane rats . It is generally assumed that the ancestors of the guinea pig relatives crossed the then much narrower Atlantic by swimming on driftwood. The early Oligocene is considered to be the point in time for colonization of South America , the oldest fossil finds come from Chile and are around 31 million years old.
At that time, as during most of the Cenozoic , South America was isolated from the other continents, so that a very special mammal fauna developed there, comparable to the situation in Australia . Originally there were only three mammalian taxa: the marsupial mammals , represented by the opossum rats , the paucituberculata and the sparassodonta (" pouch hyenas"), the now extinct South American ungulates (meridiungulata) and the collateral animals . (A few million years after the guinea pig relatives , the New World monkeys also reached South America in a similar way.)
For this reason, the guinea pig relatives were able to occupy some ecological niches that are untypical for rodents and are only found in this form in this group. So there were gigantic forms: the Capybara, the largest rodent , still belongs to this group, extinct forms such as Phoberomys even reached the size of hippos . Long-legged forms with hoof-like toes also developed, such as the agoutis and the pampas hares , which to a certain extent form the ecological equivalents of the artifacts . In addition, there was also the formation of mice - or rat-like animals, and - as with the other rodents too - tree and soil-dwelling species and also underground burrowing species emerged.
Around 2.5 million years ago, the land connection between North and South America was closed with the Isthmus of Panama , and there was a large-scale exchange of fauna . Numerous mammalian taxa now immigrated to South America, with some fatal consequences for the endemic fauna: many groups died out, but the guinea pig relatives were less affected than other taxa. In return, some species that were previously restricted to South America were able to expand their range to Central America, whereas only one species made it to North America with the Urson .
With the colonization of America by humans and especially since the immigration of Europeans, the American fauna has been greatly changed. Some species, especially those endemic to the Caribbean islands , have become extinct, including the whole family of the giant hatias as well as some representatives of the spiny rats and tree rats .
External system
The guinea pig relatives (Caviomorpha) form an ancestry group within the Hystricognathi . Usually they are compared to the families of the sand graves (Bathyergidae), reed rats (Thryonomyidae) and rock rats (Petromuridae), united as Phiomorpha , whose common sister group then form the porcupines . A graphical representation of the possible external family relationships looks like this:
| Hystricognathi |
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Except for the tree prickers, the guinea pig relatives were grouped together in the Mus genus in Carl von Linné's Systema Naturae in 1735 . This genus, which today corresponds more to the rank of a family or order, also contained squirrels and mice relatives . The tree prick, however, was united with the porcupine in the genus Hystrix .
While most guinea pig relatives have long been believed to be related, the tree prickers continued to be frequently placed outside this group. Older studies on muscles, arteries, skulls and teeth suggest that they represent an early sideline of the porcupine relatives and thus do not belong to the guinea pig relatives. Studies on parasitology also contradict a common ancestry; accordingly, the guinea pig relatives have several independent ancestors within the rodents. More recent molecular genetic studies, however, support the descent from a common ancestor and the development from the porcupine relatives.
Internal system
The relationships within the guinea pig relatives are still largely unclear. The system used here with its subdivision into four superfamilies is based on recent molecular genetic studies. The following families are currently distinguished:
- Superfamily tree spikes (Erethizontoidea)
- Tree prick (Erethizontidae) including the bristle tree prick
- Superfamily guinea pigs (Cavioidea)
- Pakas (Cuniculidae)
- Agoutis and Acouchis (Dasyproctidae)
- Guinea pigs (Caviidae) including the giant rodents
- Superfamily chinchillas (Chinchilloidea)
- Dinomyidae
- Chinchillas (Chinchillidae)
- Superfamily Trugrattenverbindungen (Octodontoidea)
- Chinchilla rats (Abrocomidae)
- Trug rats (Octodontidae)
- Comb rats (Ctenomyidae)
- unnamed taxon
- Quill rats (Echimyidae)
- Beaver rats (also nutrias; Myocastoridae)
- Tree rats (also Hutias; Capromyidae)
- Giant hatias (Heptaxodontidae); Recently extinct, systematic classification uncertain
The Eocardiidae , which became extinct in the late Miocene, are also classified under the guinea pig relatives.
In the past, the individual groups were repeatedly combined in different ways, so that different definitions can be found in the literature for each of the above-mentioned superfamilies. The definitions of some families have also changed over time. The relationships between the individual superfamilies are not yet certain; the following illustration follows Heritage et al. (2016):
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The porcupines are often not classified in the guinea pigs-like because of their different morphology. Together with the Pakaranas, due to related endoparasites, a relationship with porcupines and spring hares was assumed. The assignment of the bristle tree prick is also unclear. Here they are placed with the tree cutters; in other classifications they are classified as a subfamily with the sting rats.
The guinea pig-like form a well-defined group with the exception of the Pakaranas; This is supported by both morphological and molecular genetic studies. The agoutis and acouchis are classified as a subfamily next to the pakas or run as an independent family. Now integrated into the guinea pigs, the giant rodents have long been regarded as their sister group.
The Pakaranas are sometimes placed close to the tree cutters, with whom they share a fusion of the second and third cervical vertebrae and other morphological features; also both are attacked by pinworms of the genus Wellcomia . Tooth patterns, on the other hand, indicate a relationship with the guinea pig-like; A close relationship was assumed especially with pakas, agoutis and acouchis. The relationship with the chinchillas is also supported by tooth samples and molecular genetic studies.
The chinchilla rats are often placed near the chinchillas. Molecular genetic investigations clearly contradict this and, like tooth features, rather show a relationship with the turtle rat-like. Her closest relatives within this group are not known. The crested rats are often placed as a subfamily to the trug rats. This is based on many features that are assumed to be derived together, such as the kidney-shaped molars.
Barbed rats , beaver rats and tree rats form a related group that has been well documented by studies of teeth and muscles as well as molecular genetic studies. The beaver rats are assigned to either the barbed rats or the tree rats as an independent family or as a subfamily. Immunological and molecular genetic studies speak in favor of the assignment to the quill rats. The tree rats were also occasionally placed as a subfamily to the sting rats.
The extinct giant hatias are often put close to the chinchillas because of their similar molars; but other features of the teeth, such as tooth patterns, indicate a relationship with the tree rats. In addition, it cannot be ruled out that the giant hatias themselves do not form a kinship group.
designation
Carl von Linné assigned the guinea pig relatives to the two genera Mus and Hystrix , which today only contain distant relatives. The first genus still classified in this group today was named by Peter Simon Pallas in 1766 as Cavia , which refers to the caves (Latin: "cavi") sought as refuge by some species. Caviomorpha, the name still valid today for the guinea pig relatives, was introduced in 1955 by Albert Edward Wood ; other sources name Lucas Kraglievich (1930) as the author. Dan Bryant and Malcolm C. McKenna introduced the name Caviida in 1995.
literature
- Erich Thenius, Erna Mohr , Dietrich Heinemann (eds.): The guinea pig relatives . In: Bernhard Grzimek et al. (Ed.): Grzimeks animal life . Mammals 2 . Kindler Verlag, Zurich 1969, pp. 413–447, ISBN 3-8289-1603-1 (ISBN refers to the paperback edition from 2001).
- Thomas S. Kemp: The Origin & Evolution of Mammals. Oxford University Press, Oxford 2005, ISBN 0-19-850761-5 .
- Charles A. Woods, C. William Kilpatrick: Infraorder Hystricognathi. In: Don E. Wilson, DeeAnn M. Reeder (Eds.): Mammal Species of the World . 3rd edition. Johns Hopkins University Press, Baltimore 2005, pp. 1.538-1.600, ISBN 0-8018-8221-4 .
- Malcolm C. McKenna, Susan K. Bell: Classification of Mammals: Above the Species Level . Columbia University Press, New York 1997, ISBN 0-231-11013-8 .
- Poux et al .: Arrival and Diversification of Caviomorph Rodents and Platyrrhine Primates in South America. In: Systematic Biology . No. 55, 2006, pp. 228–244 ( PDF ; 4,342 kB).
- Juan C. Opazo: A Molecular Timescale for Caviomorph Rodents (Mammalia, Hystricognathi). In: Molecular Phylogenetics and Evolution. No. 37, 2005, pp. 932-937 ( ISSN 1063-5157 ; PDF ; 405 kB).
- Dorothée Huchon, Emmanuel JP Douzery: From the Old World to the New World: A Molecular Chronicle of the Phylogeny and Biogeography of Hystricognath Rodents . In: Molecular Phylogenetics and Evolution. Vol. 20, No. 2, August 2001, pp. 238-251 ( PDF ; 146 kB).
Individual evidence
- ↑ a b Heritage S. et al. 2016. Ancient phylogenetic divergence of the enigmatic African rodent Zenkerella and the origin of anomalurid gliding. PeerJ 4: e2320; doi: 10.7717 / peerj.2320